Extreme Heat

Extreme heat is defined as weather that is “substantially hotter and/or more humid than average for a location at that time of year” (Hazard Identification and Risk, 2011, p. 31) The Heat Index, which measures the “apparent temperature” when considering both air temperature and humidity, is used by organizations like the National Weather Service to identify extreme heat days. Extreme heat is particularly dangerous when occurring for a prolonged period (known as a “heat wave”).

Periods of extreme heat can cause serious injury or death to exposed populations, especially the elderly, infants, transient populations, persons with physical and mental impairments, and those without access to air conditioning or social services. Extreme heat is also associated with increased demands for electricity and water, and can potentially stress local and regional infrastructure and services. Prolonged periods of extreme heat can have negative impacts on farming and livestock, and may lead to algae blooms that increase the risk of fish kills. Extreme heat can also have a negative impact on health and productivity, with a direct impact on economic activity and travel. Warming temperatures and extreme heat have also been shown to have negative impacts on forests, aquatic ecosystems, and wildlife and fish populations (Rocky Mountain Forests, 2014).